Ignore last...having thought about it for 10 minutes the obvious thing
to do is to add the drives back and allow the array to rebuild
offline......

For the following reasons....

1.  e2fsck -f -n /dev/mdxx reports all the data appears intact and
that was what I believed anyway based on the information available to
me.

2.  To finish the backup will take 30+ hours, that's 30+ hours of risk
time where a single drive failure will compromise the data set.

3.  To 'add' the missing drives back into the array and allow the
rebuild will take about 10 hours (based on my previous experience
building this array), therefore the lower 'risk' course of action is
to rebuild the array, then and only then, to restart the backup.
There's over 20 hours less risk doing it this way.

I realise I could do the two concurrently but I'd rather keep the
array 'destressed' as much as possible until I've got at least one
level of resilience restored.

Having now added the drives back in as 'spares' mdstat is telling me a
little over 12 hours to do the rebuild so it's now finger crossing
time time then.

Thanks for the help and advice....and most of all the confirmation my
approach was the correct one.



On 21 September 2015 at 02:32, Another Sillyname
[off-list ref] wrote:

OK

The array has come back up...but showing two drives as missing.

mdadm --query --detail /dev/md127/dev/md127:
        Version : 1.2
  Creation Time : Sun May 10 14:47:51 2015
     Raid Level : raid6
     Array Size : 29301952000 (27944.52 GiB 30005.20 GB)
  Used Dev Size : 5860390400 (5588.90 GiB 6001.04 GB)
   Raid Devices : 7
  Total Devices : 5
    Persistence : Superblock is persistent

  Intent Bitmap : Internal

    Update Time : Mon Sep 21 02:21:48 2015
          State : active, degraded
 Active Devices : 5
Working Devices : 5
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 512K

           Name : arandomserver.arandomlan.com:1
           UUID : da29a06f:f8cf1409:bc52afb2:6945ba08
         Events : 285469

    Number   Major   Minor   RaidDevice State
       0       8       97        0      active sync   /dev/sdg1
       1       8       49        1      active sync   /dev/sdd1
       2       8       65        2      active sync   /dev/sde1
       3       8       81        3      active sync   /dev/sdf1
       8       0        0        8      removed
      10       0        0       10      removed
       6       8      129        6      active sync   /dev/sdi1

Data appears to be intact (haven't done a full analysis yet).

Does this mean I should add the 'missing' drives back into the array
(one at a time obviously)!.

Also doesn't this mean I'm horribly exposed to any writes now as this
would move the current 5+2 further out of 'sync' with each other thus
meaning any further short term fail could smash the data set totally.

I'm minded to stop any writes to the array in the short term and
continue just doing the backup (this in itself will take about 30+
hours).

Ideas and observations?



On 20 September 2015 at 10:54, Mikael Abrahamsson [off-list ref] wrote:

quoted

On Sun, 20 Sep 2015, Another Sillyname wrote:

quoted

Thanks

Would you.....

mdadm --assemble --force --scan

or

mdadm --assemble --force /dev/mdxx /dev/sd[c-i]1

This last one is what I use myself.


--
Mikael Abrahamsson    email: swmike@swm.pp.se